The member states provide an online system letting sellers register in all member states and any other state using the system. By registering, a seller agrees to collect and remit sales and use tax on all taxable sales into the states it chose; a state's withdrawal or expulsion does not relieve the seller of remitting tax collected for it before or after. A state where the seller already had to register may ask for more information, or the seller may register directly with it. No member state, nor a state that withdrew or was expelled, may use registration through the central system and collection in member states as the sole factor in deciding whether the seller has nexus for any tax at any time.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.